Proteolipid protein (PLP) is the major structural protein of the central nervous system (CNS) muelin. Techniques have been developed to isolate pure and immunologically active preparations of PLP from rat brain myelin. Specific precipitating antibodies to myelin PLP have been produced, and immunohistochemical techniques were used to demonstrate its exclusive locadization to oligodendrocytes and the myelin sheath. An extremely sensitive radioimmunoassay for PLP has been developed, and it will be used for quantitation of this antigen in neuraa tissues in normal mice and in mutant miie with defective myelination. Antiserum to PLP will be used to examine the appearance of this protein by innunofluorescence in the brains of Jimpy and Quaking mice during development. Similarly, studies on the synthesis and degradation of myelin PLP will be carried out in the brains of Jimpy and Quaking mice to determine if there is a defect in transport from glial cells to myelin or accelerated degradation of myelin PLP in these animals. Studies are in prooress to develop a cell-free system in vitro for the synthesis of PLP using highly purified antigen and antibodies. It is possible to maintain constant specific radioactivity of (14 C) tyrosine in the plasma and brain for a period of 10 days in adult mouse. Methods have been standardized to prepare myelin subfractions from the adult mouse brain and isolate pure preparations of PLP from light and heavy myelin in order to determine if there is a differential turnover of this protein. The availability of an extremely sensitive and fluorescent reagent will allow us to isolate PLP from whole brain and myelin and determine if saturated and unsaturated fatty acids are linked to this protein. Development of a column chromatographic method for the bulk isolation of myelin PLP will facilitate elucidation of the macromolecular structure of this protein.